The stufferbox crimping process is predominantly used in the production of staple fibers. The initial step in the production of staple fibers is to produce very thick tows, for example by two or more filament bundles being withdrawn from cans, converged to form a tow and conjointly led to a stufferbox, as described for example in EP 0 139 832 B1. The total linear density of the tows is up to 4,000,000 dtex.
Melt spinning processes, which predominantly supply fibers for such stufferbox crimping processes and operate at spinning speeds of 500 m/min or higher, involve direct drawing to a draw ratio of 4:1 to produce a drawn tow at a speed of at least 2000 m/min. These tows can therefore usually not be fed directly to the further processing stages, which frequently operate at appreciably lower speed; they are therefore interveningly stored in cans for example. Moreover, the linear density of such tows is too high for some further processing purposes, especially for producing textile hygiene products.
The processes discussed above require stufferbox crimpers as described for example in EP 0 139 832 B1 and DE 34 40 975 A1.
Fluid-absorbing hygiene articles usually contain acquisition layers consisting of fibrous non-woven material, for example a carded fiber web. EP 0 937 792 A1 describes a process where this absorbing fibrous layer is formed from a thin tow of continuous filaments.
This European patent application does not mention stufferbox crimping, nor the total linear density of the tows used therein nor any process whereby the filament tow mentioned therein is actually to be produced.
Although there are already a whole series of processes in existence for stufferbox crimping fiber tows there is still a need for improved, more flexible processes which make it simple to conform to the requirements of downstream operations.